Internal combustion engine



Oct. 27, 1964 ((uurcuuu T. w. KUNZOG INTERNAL COMBUSTION ENGINE FiledJan. 26, 1962 INVENTOR. Theodore W Kunzog His Afiorney United StatesPatent 3,153,990 INTERNAL COMIEIJS'IIQN ENGINE Theodore W. Kunzog,Dayton, @hio, assignor to General Motors (Iorporation, Detroit, Mich, acorporation of Delaware Filed .Ian. 26, 1962, Ser. No. 169,053 6 Claims.(Ci. 92169) This invention relates to internal combustion engines andother devices using reciprocating pistons and is particularly concernedwith cylinder liners of various types for use in such engines.

In many types of internal combustion engines, and particularly smallhorsepower engines and two cycle engines, the engine is air cooled byfins cast directly on a cylinder block. Engines of this type frequentlyuse cylinder liners for the block since the material thereof is aluminumor some suitable diecasting metal. The liners may be cast directly inplace or the liners may be removable and replaceable.

One type of liner for engines of this character is disclosed in myPatent 3,000,370, granted September 19, 1961. In this patent a porousmetal line is shown which includes an interfitting portion for carryingvalve seats and valve guides so that all of the parts arepredeterminately arranged prior to the time that the block is casttherearound. In this instance the liner is not replaceable.

In application 109,959, filed in the name of Anton F. Erickson on May15, 1961, now Patent No. 3,033,- 183, granted May 8, 1962, and assignedto the assignee of the present invention, a short cylinder liner isdisclosed and claimed which may be removably positioned within any ofthe usual types of cylinder blocks where a liner is desired. The basisfor the invention is the specific length of the liner which onlyencompasses that portion of the cylinder wall which is traversed by thepiston rings. a

The present invention is directed to improvements over both of theseinventions and wherein the cylinder liners may be cast in place or maybe made removable with respect to the block as desired. It is to beunderstood that while these liners are particularly adapted for aircooled engines and the like that this is not a limitation and that theliners as disclosed herein may be used in connection with many types ofinternal combustion engines, pumps and similar devices which usereciprocating pistons.

It is, therefore, an object of this invention to provide an improvedcylinder liner for an internal combustion engine and the like,comprising a cylindrical metal sleeve of a strong sheet metal materialand having a porous metal surface thereon.

A further object of the invention is to provide a method for making sucha liner wherein long lengths of sintered strip material are formed,which strip is then wound around a mandrel to form a tube having aspiral seam which is welded to form a continuous tube and thereafterliners of the desired lengths are cut from the tube by separating thetube in a plane perpendicular to the longitudinal axis thereof.

A still further object of this invention is to provide a liner andmethod for making same from a flat strip of sheet metal having sinteredmetal powder at one surface thereof wherein the strip is formed to acylindrical form and includes a flange at one end thereof and whereinports may be punched directly in the flat sheet prior to the formationof the cylindrical liner for 3,153,990 Patented Oct. 27, 1964 'valvingwhen the liner is to be used in connection with 'two cycle engines.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein preferred embodiments of the present invention areclearly shown.

In the drawings:

FIG. 1 shows a section of a strip of strong metal hav ing a sinteredmetal liner on one surface thereof.

FIG. 2 is a cylinder liner made from a segment of the strip shown inFIG. 1 with the abutting edges thereof welded together to form acylindrical sleeve. FIG. 2A shows a preferred V-cut seam.

FIG. 3 is a modification of the liner shown in FIG. 1 whereincircumferential grooves are formed directly in the liner for increasingthe surface thereof which grooves may be used for cooling and/or forpositioning the liner when the same is to be cast directly in a block.

FIG. 4 is a variation of the liner shown in FIG. 2 wherein a flange isprovided at one end thereof and wherein ports are shown in the wall ofthe liner.

FIG. 5 is a diagrammatic view showing another method of making the linerwherein the strip with the porous metal surface at the inside surfacethereof is wound spirally to form a continuous tube.

FIG. 6 is a view of a liner cut from the tube formed in FIG. 5 at thedot-dash line portions thereof.

Strip stock from which the liner may be made can be produced by any ofseveral well known processes. For example, Koehring et al. Patent2,158,461 discloses a method for producing composite strip materialincluding a steel strip having a pressed and sintered layer thereon ofporous metal. In Koehring Patent 2,198,253 another method is disclosedfor sintering metal powder onto a strong metal support. In this instancethe porous metal layer produced may be sized to a desired thicknessafter sintering. Koehring Patent 2,289,658 discloses still anothermethod for producing a composite strip material utilizing a steel basewith a compacted porous metal layer thereon.

In some instances it maybe desirable to make the strip entirely ofporous'inetal without the steel backing. This is particularly true ifthe liner is to be cast in place since the porosity of the liner offersanchoring points for the cast metal. One method of producing a porousmetal strip stock without a supporting backing is shown in Marvin Patent2,341,732 wherein the metal powder is pressed directly into a strip andis sintered. All of these and many more patents disclose methods formaking a strip stock comprising a porous metal either bonded directly tosteel or without a steel backing.

Specifically, I prefer to use iron powder as the porous metal layer;This may be mixed with small .quantities of copper powder, for exampleup to 5% as a supplemental bonding agent or with ferro-phosphoruspowder. The ferro-phosphorus acts as a bonding agent and also hardensthe resulting porous metal layer. Lenel Patent 2,291,732 discloses useof ferro-phosphorus as a bonding agent. Similarily, graphite may beadded to'the iron powder. It may be added up to 2% to form materials asdesired. Againthe specific composition of the layer forms no part of myinvention since it is well known in the art that'sintered layers ofmetal may be made by. a number of processes and using a variety ofsuitable alloying agents, although theuse of these agents is not alwaysnecessary nor desired. In any event, after the strip has been formedeither with a steel backing or without, it may be cut transverselythereof as shown in FIG. 1 wherein a steel strip is shown having aporous metal layer 22 on one or both surfaces thereof. Layer 22 ispreferable in the order of .020" to .030 thick and and has beencompacted in the fiat condition to relatively high density. The strip iscut along the dot-dash lines 24 which produce a developed length desiredfor the cylinder. The strip is then formed into a cylinder 26 and isbutt welded along the abutting edges 28. The butt weld is machined offso that a smooth surface is provided. In some instances it may bedesirable to form annular grooves in the strip either for cooling orkeying purposes. Grooves are shown at 30 in FIG. 3 wherein a linersimilar to the liner of FIG. 2 is shown except for the addition of thegrooves. In FIG. 4 another type of liner is shown that may be usedspecifically in two cycle engines. In this instance ports 3 are punchedin the developed lengths of the material prior to forming the cylinder32. Similarly, a flange 36 may be applied to the cylinder liner eitherby welding or by forming, if the flange is to be of relatively minorextent. This flange aids in positioning the liner in the block.

In all of these embodiments the liner has been formed from flat stock.Referring also to FIG. 5, another method of forming is shown wherein amandrel 40 having a desired diameter is used. A strip 42 of undeterminedlength, and either formed from a porous metal or from steel strip havingporous metal at one surface thereof, is

spirally wound around the mandrel so that the edges thereof are in tightabutting relation. The strip is wound so that the porous metal is incontact with the mandrel. This provides a continuous process for forminga spirally wound tube. The seam thereof may be progressively welded ifdesired, as the tube is formed and may be progressively machined to forma smooth outer surface on the tube. Suitable lengths of the tube are cut05 for ease of handling and cylinder liners may be severed therefrom bycutting the tube into the desired lengths, for example, on dot-dash line44 to form a cylinder liner 46, as shown in FIG. 6 wherein the seam 43thereof runs spirally of the liner.

Of course, operations involving formation of a continuous tube areusually carried out on a relatively large scale operation since it isapparent that the equipment is more costly, although once provided, theultimate cost of the liner is reduced.

A specific example, stock used for a liner is as follows. Strip stock.060 thick S.A.E. 1020 steel was prepared with a porous metal layerthereon having a finished thickness of .040 thick. This layer was madefrom reduced oxide iron powder and had a relatively low porosity whereinthe density in the finished state was in the order of 6.256.5 gm./cc.and contained 4% carbon. The strip was cut to size and rolled into aliner 4" long and 2 /2 inside diameter. It is apparent that thesefigures may vary widely in accordance with the liner desired and thepurpose for which the liner is to be used.

It is to be understood that in some instances the seam does not requirewelding. If the edges are ground mere abutment is suflicient,particularly when the sleeve is to be cast in place. It may be desirableto spot weld the seam at the top and bottom and outside of that portionwhere the piston rings will slide. This maintains the cylinder with itsedges in abutting relation during placement thereof. In general, theporous metal portion will absorb oil, some of which will carbonize andthen any oil leakage through the seam will quickly be stopped. I preferto test liners in a particular application to determine whether the seamrequires welding.

In this connection FIG. 2A shows V-cut seam wherein the abutting edgesare cut at an angle of about 30- 45 from the vertical, this offers spacefor welding metal when required.

Liners of this character, whether porous metal and steel or plain porousmetal, are highly useful since they tend to take up some oil which has alubricating elfect on cylinder walls. Further, the porosity of the lineris limited since in use, carbon formed in the cylinder is picked up bythe pores of the liner and tends to seal the same. In some instances itmay be desirable to lubricate the porous metal with M05 This yieldsexcellent lubrication while being capable of withstanding thetemperatures within a cylinder.

When the liner is to be cast in place, I prefer to use a fully porousmetal liner since this aids in keying the liner to the cast material. Ofcourse, a steel liner having porous metal on both sides thereof may alsobe used but is more expensive to fabricate.

It is apparent from the foregoing that the liner disclosed overcomesmany of the past manufacturing difiiculties apparent in patents andapplications mentioned herein. These difiiculties are mainly found inthe manufacturing of porous metal liners of any substantial length.Briquetting operations on any such liners are difiicult to control inorder to obtain a uniform density throughout the length of the liner. Byfollowing the teachings of my invention it is possible to produce such aliner at the lowest possible cost. Furthermore, since the liner isinitially formed from strip material, expensive briquetting dies are notrequired, it merely being necessary to use different mandrels. This alsoreduces the cost of the liner. One additional advantage of the presentliner is that the porous metal may be made extremely thin particularlyif it is supported on steel and this reduces the cost of the materialused wherein the strip material may be manufactured by following theteachings found in the aforementioned patents.

Since the liner is formed from strip stock it is a simple matter tofinish the surface either by boring, grinding, or any other suitable andwell known machine operation. This can be done on automatic equipmentwhich further reduces the cost.

While the embodiments of the present invention as herein disclosedconstitute preferred forms, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. In a method for making cylinder liners for internal combustionengines and the like, the steps comprising; providing a length of sheetmetal having a porous ferrous metal layer coextensively bondedmetallurgically to one surface thereof said layer having a density aboveabout 6.25 grams per cc., forming the strip into a cylindrical shapewith the porous metal layer on the inside of the cylindrical shape,welding the seam on one side only of said shape for permanently joiningthe sheet metal and then finishing the porous metal inner surface to aprecision dimension.

2. In a method for making cylinder liners for internal combustionengines and the like, the steps comprising; providing an indeterminatelength of sheet metal having a porous ferrous metal layer coextensivelybonded metallurgical to one surface thereof said layer having a densityabove about 6.25 grams per cc., forming the strip with the porous metallayer on the inside surface thereof into a long cylindrical shape havinga spiral abutment, welding the abutment on the outside surface onlythereof for forming a long length of cylindrical tubing, progressivelycutting the tubing perpendicularly of its longitudinal axis for forminga plurality of cylindrical liners of the desired length, and thenindividually finishing the internal surfaces of each of said liners.

3. The process as claimed in claim 1 wherein annular cooling grooves arerolled into the cylinder above and/ or below the working surfacethereof.

4. The process as claimed in claim 2 wherein annnular cooling groovesare rolled into the individual cylinder liners above and/or below theworking surface thereof during said finishing step.

5. The method claimed in claim 1 including the added step of punchingport holes in the strips prior to forming the same into cylindricalshape.

6. A cylinder liner having an internal combustion engine comprising incombination a cylindrical sheet steel sleeve including an abutted seamextending generally longitudinally thereof and throughout the length ofthe sleeve, said seam being welded on the outer surface only of thesleeve, and a coextensive inner layer of porous ferrous metal bondedcoextensively and metallurgically to the sleeve and comprising sinteredferrous metal having a density of above about 6.24 grams per cc., saidporous metal lining including up to 4% carbon.

References Cited in the file of this patent UNITED STATES PATENTS AldenAug. 2, 1887 Schattanek Dec. 8, 1931 Bell Feb. 19, 1935 Sanders Feb. 15,1938 Koehring et a1 May 16, 1939 Colwell et a1. Jan. 28, 1947 BartlettDec. 7, 1954 FOREIGN PATENTS Great Britain Jan. 16, 1947

1. IN A METHOD FOR MAKING CYLINDER LINERS FOR INTERNAL COMBUSTIONENGINES AND THE LIKE, THE STEPS COMPRISING; PROVIDING A LENGTH OF SHEETMETAL HAVING A POROUS FERROUS METAL LAYER COEXTENSIVELY BONDEDMETALLURGICALLY TO ONE SURFACE THEREOF SAID LAYER HAVING A DENSITY ABOVEABOUT 6.25 GRAMS PER CC., FORMING THE STRIP INTO A CYLINDRICAL SHAPEWITH THE POROUS METAL LAYER ON THE INSIDE OF THE CYLINDRICAL SHAPE,WELDING THE SEAM ON ONE SIDE ONLY OF SAID SHAPE FOR PERMANENTLY JOININGTHE SHEET METAL AND THEN FINISHING THE POROUS METAL INNER SURFACE TO APRECISION DIMENSION.